Solvent refining of mineral oil



Jan. 4, 1938. D. STRYKER ET AL 2,104,379

SOLVENT REFlNING OF MINEAL OIL Filed May 1o, 1954 Patented Jan.` 4, 1938 A 2,104,379 soLvEN'r REFINING oF MINERAL om Daniel Stryker, white Plains, ana James n. Grahame, Mount Vernon, N. Y., assignors to The Texas Company, New York, N. Y., a. corporation of Delaware Application May 10, 1934,-Serial No. 724,852 1 Claim. (Cl. ISS- 18) fil like containing asphaltic, naphthenic and parafflnic constituents, including wax, wherein the oil is treated with a solvent adapted to precipitate the asphaltic constituents, then extracted with an l extraction'solvent adapted to separate and re,

move the naphthenic constituents of low lubricating value, and thereafter the extracted oil is dewaxed.

The invention contemplates effecting the rey l5 moval of the asphaltic, naphthenic and wax constituents through the agency of a common solvent.

A solvent suitable for this purpose is one which is adapted to precipitate the asphaltic constituents while retaining the remaining oil in solution,

Z0 and which is also adapted to serve as a diluent during the subsequent extraction and dewaxing steps. Such a solvent may comprise, for example,

a light petroleum fraction of the character of propane, or which may comprise a mixture of 5 light hydrocarbons, such as ethane, propane and butane.

, The invention, therefore, comprises mixing a wax-bearing lubricating cil fraction of crude oil with a light petroleum fraction of the character of propane, in sufficient proportion to precipitate the asphaltic constituents of the oil, while retaining the wax and remaining oil in solution. The precipitated asphaltic constituents are then removed from the dilute mixture, following which the dilute mixture is subjected to extraction with an extraction solvent having a selective action as between naphthenic and paranic constituents of the oil of the character of furfural, acetone, nitrobenzene, etc.

40 The presence of the diluent in the oil under going extraction serves to bring about a more effective and intimate contact between the extraction solvent and the oil. It'also facilitates the resulting separation of the oil and solvent into naphthenic and paraflinic layers. These resulting layers are separately removed from the extracting zone and the parainic or railinate layer maythen be dewaxed. Dewaxing of this raffinate fraction may be readily effected, since it is already in a dilute condition. Furthermore,

it also contains a proportion of the extraction solvent which acts as an anti-solvent for the wax. If desired, additional quantities of diluent and anti-solvent may be added thereto to further facilitate the removal of wax. 'Ihe quantities of of lubricating oil from mixed-base crudes and the' diluent and wax anti-solvent liquid thus added are suilicient to form a solvent liquid mixture having selective action as between oil and wax at temperatures of the order of 0 F.

The actual removal of the wax may be effected by any of the well known methods, including centrifuging, settling or illtering, and where ltration is used the wax may be filtered from the mixture in the presence of a suitable iilter-aid material.

An important advantage of'our invention resides in effecting removal of the asphaltic and naphthenic bodies prior to dewaxing. This is particularly true where the dewaxing is carried out by filtration methods. 15

There are certain constituents of the oil removed along With the asphaltic and -naphthenic bodies, which apparently inhibit the separation of the Wax in a readily lterable form,` and which also impede subsequent filtration. These con- 20 stituents are of such a nature that they may not be suiciently removed by extraction alone, or by the deasphaltizing step alone. It has been found advantageous, therefore, to subject the oil to a deasphaltizing as well as a solvent extraction -25 treatment prior to dewaxing.

In order to more clearly describe the invention, reference will now be made to the accompanying drawing forming a part of the specification. e

The oil to be refined, for example, a viscous waxbearing residual lubricating oil fraction, such as derived from Mid-Continent crude, is conducted from a tank I through a pipe 2 to a mixer 3. Li-

. pane precipitate from the mixture and are removed through an outlet 1,

After removal of the asphaltic material, it may be desirable, in some instances, to either remove part of the propane diluent, or to add a further 50 quantity, depending upon the character of the stock being treated.

The remaining portion of wax-bearing oil and propane is `then conducted from the settler 6 through a pipe 8 to an extracting chamber 9. 65

This extracting chamber is advantageously of the countercurrent tower type wherein the dilute oil is introduced to the lower portion of the chamber and caused to rise upwardly therethrough. The extraction solvent -is introduced to the upper portion of this chamber and descends downwardly therethrough in directv contact with the upwardly moving body of dilute oil. The chamber may or may not be provided with contacting means, such as bales or other packing material, as desired. l

The extraction solvent, which in this instance comprises furfural, is conducted from a tank I0 through a vpipe Il to the upper portion of the chamber 9, and may be introduced thereto at a temperature of around 100 F., or at higher temperatures of around 200 to 300 F.

The temperature of the furfural entering the chamber may be regulated by its passage through a suitable heat exchanger IIa. The proportion of furfural to oil mixture may comprise about two parts of furfural to one part of mixture. Either smaller or larger proportions of .furfural to oil may be used, depending upon the degree of extraction desired, as well as upon the nature of the oil undergoing treatment.

Due to the selective action of the furfural upon the oil, the mixture separates into fractions respectively rich in naphthenic and paraii'inic constituents. The naphthenic constituents, clissolved in furfural, are removed as extract from the bottom of the chamber 9 through an outlet I2.

The parainic constituents, including wax mixed with a large amount of propane and some iurfural, are removed as raffinate from the top of the chamber 9 through a pipe I3.

The rainate is then conducted through a mixer I4 and a chilling coil I5, wherein the mixture is chilled to temperatures of the order of 0 F. and below in order to solidify the wax. It may be desirable, prior to chilling, to increase the amount of diluent present, in which case additional quantities of propane are conducted from the tank 4 through a pipe I6 to` the inlet of the mixer I4, wherein it is mixed with the raffinate.

Likewise, additional quantities of furfural may be. added to the rainate by line I'I prior to its introduction to the mixer for the purpose of rendering the solvent mixture less soluble towards the wax.

Instead of using furfural as the anti-solvent, it is contemplated that other selective solvent liquids, such as acetone and methyl ethyl ketone, may be used.

In some cases, it may be unnecessary to add additional anti-solventliquid since the raffinate, as it leaves the extraction chamber 9, may contain sufficient furfural to serve as a wax anti-solvent.

The chilled wax-bearing mixture is then conducted through a pipe I 8 to a filter I9 wherein the wax is separated in the form of a filter cake. The resulting filtrate is removed from the filter and collected in a tank 20, while theiilter cake is accumulated in the tank 2|.

1f 1t is desired to use a inter-aid material, the l chilled mixture may be conducted from the chilling coil I5 directly to a mixer 22, wherein it is mixed with filter-aid material, such as fullers earth, diatomaceous earth, and the like, from a storage bin 23. The resulting mixture, containing suspended wax and filter-aid material, is then conducted to the lter I9 wherein the wax is separated in the presence of the filter-aid material.

The solvents contained in the iiltrate and wax may be removed by distillation or in any other suitable manner, and recovered for re-use.

The invention is not restricted to the particular operating conditions described in the foregoing example. The temperatures therein set y forth may be varied, depending upon the nature of the oil undergoing treatment. It is contemplated that a closed system will be used capable of withstanding pressures sufficient to maintain the propane or other normally gaseous diluent petroleum fraction in a liquid state.

The invention is not limited to the treatment of residual lubricating oil fractions,` as above described, but is also adapted to the treatment of distillate lubricating fractions. It is also contemplated that the process may be applied to viscous Wax-bearing cylinder stocks.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claim.

We claim:

In the process of manufacturing lubricating oil from residual lubricating oil stock containing large amounts of wax, such as derived from Mid- Continent crude, the method comprising diluting the wax-bearing oil with propane in suiiicient quantity to precipitate the asphaltic constituents `while retaining the remaining oil and Wax in sotemperature in the range Aof 200 to 300 F. Whereby the mixture is separated into a raflinate phase comprising Wax and liquid paraflinic constituents of the oil, propane and a substantial amount of furfural, and an extract phase comprising naphthenlc constituents dissolved in furfural, removing the extract phase, adding a further quantity of a non-hydrocarbon solvent having anti-solvent action for wax, to said raiiinate phase to form with the retained furfural and propane a solvent mixture exerting selectiveaction as between wax and oil at a temperature of around 0 F., chilling the resultant mixture to precipitate solid hydrocarbons, removing the solid hydrocarbons so precipitated in the presence of the entire amount of anti-solvent liquid, including that initially contained in the rainate phase, and recovering the solvent from the resulting dewaxed oil.

DANIEL STRYKER. JAMES H. GRAHAME. 

